Lightly grease a 9x13 or 9x9 pan. In a large bowl combine the pretzels, chex, toffee bits, and chocolate chips.
In a large saucepan melt the butter over medium-low heat. Add the marshmallows and stir until melted completely. Remove from heat. Stir in the chex mixture until everything is coated and the chocolate starts to melt (it doesn't have to melt all the way).
Pour into the prepared pan. Sprinkle with sea salt and let cool for 15 minutes. Cut into squares and enjoy!